It depends on how much volume you've been doing. There's no question that if you run it should be incredibly easy, but if you're doing a marathon on 40 miles/week, then no run is going to be easy enough. If you've been doing 120, then you probably need a few miles to feel even semi-normal. I'm a high mileage guy, and I've always done 7, 5, 3, in the last three days before a marathon. The 5 will usually have 2 miles that are within 30 seconds/mile of MP, just to get my heart actually beating. The 3 is a shuffle with a couple of 100 meter "strides" at no faster than HMP. Immediately after the 3, I do a 10 minute yoga routine (no deep stretches), eat all the pancakes, then put my legs up for the day.